Monday, June 04, 2007

Swap: USDM vs JDM

this applies for EJ20(G,K,T,05, 07, etc)

if you dont know how to work on a car, please refer to the trusty FSM (factory service manual). A subaru is simple enough that with $100 worth of hand tools you can do anything.

You can find downloads for the 2002 USDM GDA FSM and the older JDM GC8 FSM somewhere on this website. hit the search button, i wont give it to you because i dont know where it is.

so what you need to know.

#1. All imprezas are almost fulley interchangable, All motors will fit each other, All transmission will fit each other. You may have to convert things to make them totally compatible, BUT they will fit - provided you do the proper monkey work and have the right parts.


can i put a ej205 2005 WRX engine on my 1994 FWD transmission??
Can i put a 2001 AWD gearbox on my 1993 EJ18 engine??
etc, etc, etc

#2. transplanting the proper bits from your setup is rquired -


problem: i wish to put a 1998 DOHC Ej25 engine on my FWD 1995 automatic impreza
solution: get EJ25 converted to 95 EJ18 wiring harness, then bolt up COMPLETE automatic parts to it (torque converter plate, torque converter etc)

#3. Can i convert my FWD to AWD? Can i convert my AWD to FWD? can i convert my FWD/AWD to RWD

-YES. Look for the proper FAQ to find the solution.

Steps in logistically doing your conversion:

1. find FSM for your existing setup and for whats going into it.
i.e.- if putting 1996 Sti-RA EJ20 into 2003 USDM 2.5RS, get both FSM. you need all the info you need.

2. Figure out the logistical scope of your project; how much $$$ you need to blow, how much $$$ you have to blow, how much time / manpower / tools you need and have.

3. Get all your ducks lined up - get all the parts in or slotted to arrive JIT (just in time)

4. do it.

so my secret to doing efficient (time /cash) EJ20 swap.

--my personal pervious experiance in swaps;

2002 - FWD-> awd gas tank / disc brake conversion on 93 impreza
2003 - EJ20G sti version 1 into FWD 94 EJ18 5 speed car
2003 - EJ25 DOHC into EJ18 FWD car
2003 - AWD sti version 1 gearbox into FWD EJ18 car with Hyrolic clutch conversion and turbo transmission setup / clutc
2003 - EJ20G sti engine into EJ18 FWD car - full engine bay conversion
2004 - drove car around and was happy
2005 - 1998 180SX type X blacktop into 89 Sohc S13 car
2005 - 1995 STi-RA v2 v-limited 3.9 Gearbox swap into place of 4.11 sti version 1 gearbox with Mechanical LSD rear swap into Viscous 3.9 housing
2005 - (coming up) 1995 Sti-RA V2 V-limited EJ20G entire engine bay and interior into 94 impreza with RHD conversion, electronic climate control and brake/clutch conversion for RHD......

So - going into my personal favorite conversion - what i am doing and what i put my money into (i dont listen to anyone who dosn't put their money where their mouth is)

you have a early impreza (1993-2001) i prefer early (pre 97 because its lighter). you want to have better stuff-

you need to buy a front clip. YUP. entire frekin front clip.

why the whole monty?

You actually get everything. no cut wires, nada.
You get more than you need - you can sell off anything u dont need.
Cool toys come with it -$$$$ aluminum control arms, Fatty radiator, Extra coolant overflow tank, Waterspray tank, Power steering oil cooler, Etc, etc.

if you are lucky you'll get a undamaged hood and a bumper too.

regardless, you can sell everything you dont need and it'll help offset your costs severely.

No turbo kits, no excuses, no lamearse EJ205 engine that needs $2000 thrown into it to be interesting, get the real deal. you need a JDM EJ20.

why? its the best bang for the bank. easy, Cheap (relatively), simple to do.

You can do a USDM swap, but for the expense involved ill pass. a 2004 STi would be nice with EJ257, but that is for ballers. if you get your hands on an entire USDM car dirt cheap, go for it. otherwise stick with the JDM.

have i worked on the USDM WRX? yes. i sold them before you drove them. Do i like it? my best friend has a well tuned 235 AWHP machine that i enjoy. is it good? of course its good, but $2000 of tuning bits dosnt seem a really good deal on top of the stock EJ205. not in my book. more reasons that the EJ205 isnt good enough - look at the market demand for EJ207's.

so EJ20G old skool is the best bank for the bang. comparisons with a well tuned EJ205;

will the Ej20g will be less responsive? will it make less power?

yes--IF comparing STOCK 94-96 EJ20g with hydrolic lifters, stock downpipe / flywheel/crank pulley and everything in comparison to a EJ205 standard usdm WRX motor with no cats, ECU retune to 300 CHP, aftermarket downpipe and up pipe.

Why? its obvious, response and tuning does what you pay $2000 for.

Is the older EJ20g head design inferior to the newer MEchanical ("sti version 6 head casting") ??

Yes. It is not as responsive at higher rpm's -6,000 +

does it matter? not really. not for the price differance.

What about putting an older Japenese motor in my newer car (i.e. 94-96 EJ20g into my 99 RS). Sure, why not? JDM motors only have at most 60,000 miles - it plugs in and works just fine.

all this being said, if i coould get a version 8 EJ207 to drop in my own car instead of my sti-RA version 2, id do it in a jiffy, but last time i checked - longblocks were abo9ut $8000. i dont have $8000. if you do, procede to the baller section and read somone else's FAQ.

ok. prices;

EJ20G 1994-1996 WRX front cuts can be bought for under $2500 bucks. UNDER $2500.
EJ20K 1997-2001 WRX front cuts should run you about $4500 or so.

is it worth it to go for the later ones? in my opion no, but to each his own. I'd rather spend the extra $2000 on footwork or really good food and beer, or a ticket to go to TAS.

wont the earlier clips be harder to put in my later car?
perhaps, if u are doing the wiring yourself. Otherwise the wise guru's at lachute and i-speed and the like are professionals at wiring, and it shouldnt phase them at all.

Mechanically, they are all the same.

in my book, there are 2 ways to do this conversion.

LHD and RHD.
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the LHD conversion is intense. Mad props to sam (powerlabs), and anyone else who has the guts to deal with 40 lbs of wiring hell. MAD props.

i will do any sort of monkeying mechanically, but wiring scares the ehll outa me. wiring on a SR20DET wasn't bad, but thats a walk in the park compared to a subaru.

option 1 for LHD - strip all harnesses out of your donor clip and your current car, send both to a ace shop - lachute, i-speed, rallispec, etc. Pay them $$$ for their hard work, and they will chop both harnesses and make them into one proper one for you. Will you pay for it?? YES. but its worth all the cost. I'd budget $800-$1000 for that option, i'd never do it myself.

option 2. Be an animal like yamaharocket, or powerlabs and do it yourself. when i think of this option i usually cry like a little girl. you need to pinout all the wiring, and splice things to where they need to be. not fun.

option 3. be king of monkey labor and extend all the RHD wiring. We've done this on my friends 1994 STi version 1 swap. Not fun, but easier IMO than splicing to USDM harness. figure out where everything needs to go (from looking at the JDM FSM) and then make the plugs happen there.

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RHD swap. its like a choose your own adventure book.

For a JDM EJ20 conversion, I feel that RHD swap is hte best way to do it. i'm going this route for my personal car - i put my money where my mouth is.


everytrthing fits perfectly. Every single wire, EVery sensor for electronic climate control, Every bit for power steering, AC, Everything.

what is the catch - ? you have to learn how to drive RHD, but the mail man does it, and my IQ is > than the average mailman, so you can do it too.

if you want to complain to me about RHD, go away. im not listening to it. half the world drives RHD, suck it up.

only 1 wiring plug to deal with, its R1 off the SMJ - goes to the rear bundle (fuel pump, Turn signals and the like. Besides for that, you are golden. Plug it all in and you hott.

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what about the Hydrolic pedal box and such? which gearbox should i use.

the 4.11 gearbox that comes with the JDM wrx is awesome. the USDM WRX gearbox is a POS in comparison, trust me.

you'll want to use the proper JDM gearbox with the proper JDM EJ20 motor. you'll have to make sure you have a 4.11 rear diff, LSD or not isnt important for now, deal with that later if you havnt already done it.

for RHD cars you can run the complete RHD hydrolic pedal box assembly, feor LHD you need to obtain a LHD hydrolic pedal box and clutch MC assembly. the slave cylinder is good for either LHD or RHD. Use the turbo clutch and everything in your kit - youll neeed to have all the parts, but it will all be there because you are buying a complete front clip intact.

Buy the sucker intact. FULL front half of car. the full monty.

anything i left out - please post. if you want to debate USDM vs JDM, please post on differnt thread. i'm extremely biased and have good reason to be so

if you care about emissions or need to pass inspection - find a shady smog man. or register your car in a cool state like michigan. a JDM Ej20g WILL pass california smog legit, you just neeed to have it properly installed with cats.


lryuzakilightx said...

Just have one question. I'm doing a sti swap for my 02 wrx and looking into jdm ej20 v8 but I was woundering will the usdm transmission work for jdm engine

Chris Cannella said...

Who has the wireing diagrams for pre 97 jdm gc8 impreza

Chris Cannella said...

Who has the wireing diagrams for pre 97 jdm gc8 impreza

Weldon Miguel Rodriguez said...
This comment has been removed by the author.
Weldon Miguel Rodriguez said...

is there any USDM Clutch MCs that can/will work on a RHD GC8?

Can i use the JDM rod on a USDM Cylinder or anything like that?